Carbon dots-driven spatial and electronic modulation of Ru on graphene for pH-universal hydrogen evolution reaction

The development of efficient pH-universal electrocatalysts for the hydrogen evolution reaction (HER) remains a critical challenge in renewable energy technologies. While Pt-based catalysts exhibit exceptional activity in acidic media, their performance deteriorates significantly in alkaline and neutral conditions due to sluggish water dissociation kinetics. Here, a carbon dots (CDs)-driven strategy is designed to engineer the spatial distribution and electronic structure of Ru species on graphene, achieving remarkable HER activity across the full pH range. By modulating the Ru-CDs interfacial configuration from CDs@Ru-coated to Ru&CDs-dispersed and Ru@CDs-encapsulated structures, it’s found Ru-6CDs/G exhibits excellent performance with the planar Ru&CDs arrangement. This Ru-6CDs/G catalyst exhibits ultralow overpotentials of 77 mV (0.5 M H₂SO₄), 58 mV (1.0 M KOH), and 39 mV (0.5 M PBS) at 10 mA cm-², alongside exceptional mass activities surpassing commercial Pt/C by up to 129 times. Combined experimental and theoretical analyses reveal that the Ru&CD configuration with optimal dispersion and the smallest size (~1.14 nm) of Ru nanoparticle induces a moderate d-band center position, balancing hydrogen adsorption/desorption energetics and accelerating the Volmer-Heyrovsky pathway. Density functional theory (DFT) calculations further demonstrate that charge redistribution at the Ru-CDs interface enhances H* intermediate stabilization, while COHP analysis confirms optimized Ru-H bond strength. This work not only establishes a universal design principle for metal-CDs hybrid catalysts but also provides deep insights into the electronic and spatial regulation of active sites for advanced electrocatalysis.